LET US NOT TAKE WATER FOR GRANTED

RAINWATER HARVESTING

Introduction

Water as we all know is very essential for our day to day living and that it is becoming an increasingly scarce resource. No living being, including plants can survive without water. Yet, those of us who have grown up in cities tend to take water for granted. We have not given water and the need to conserve it the importance that it richly deserves. How many of us indeed are aware that the ultimate source of water we get is the rain that falls during the monsoons?

Catching rainwater when and where it falls for use during non-monsoon months is called rainwater harvesting. This can be done in two ways: as surface water by diverting the rainwater into tanks, ponds etc. or as ground water by ingesting it into the soil. In cities, due to shrinking of open spaces, rainwater can be harvested only as ground water.

NEED FOR RAINWATER HARVESTING

Moreover, rainfall also occurs in heavy short spells of a few days or even a few hours. These characteristics of our rainfall force us not only to conserve large quantity of rainwater during these few days but also to store wherever it rains. Failure to do so results in either flooding of low lying areas or wastage by means of run off into the sea. As a result all the rainwater runs off into the road and floods the area making life miserable. It is quite possible to put all this water into the soil below with a little effort and expenditure so that the precious rainwater is not lost but becomes available for our use subsequently.

WATER IS EVERYBODY’S BUSINESS

BENEFITS OF RAINWATER HARVESTING

Rainwater harvesting replenishes the ground water table and enables our dug wells and bore wells to yield in a sustained manner.

If the ground water happens to be brackish, harvesting will reduce the salinity. In areas where the water becomes yellow due to presence of iron salts, rainwater harvesting will progressively leach out these salts leading to clean water availablity in the long run.

Flooding of low lying areas and roads can be avoided to a large extent, since rainwater that is not harvested both within the house as well as outside is mainly responsible for flooding.

WATER IS AS IMPORTANT AS FOOD

FOOD CAN BE PRODUCED : WATER TO BE MANAGED

METHODS OF RAINWATER HARVESTING

Methods of harvesting rainwater are different for different areas and therefore it is site and soil specific. It can mean anything from collecting it in a vessel to ingesting into the soil. Traditional rainwater harvesting, which is still prevalent in rural areas, was done in surface storage bodies like irrigation tanks, lakes, ponds etc. In urban areas, due to shrinking of open spaces, rainwater will have to necessarily be harvested as ground water. Hence, harvesting in such places. will depend very much on the nature of the

soil viz. clayey, sandy, rocky etc. In houses and flat complexes, rainwater falls on both the terrace (rooftop) as well as on the area all around (driveway). It is this water, which will have to be led into the ground

wherever possible.

DO NOT DROP THAT PRECIOUS DROP

PERCOLATION / RECHARGE WELL

These are constructed using cement rings readily available in the market. The diameter of these rings range from 2.5ft to 6.0ft depending on the volume of water that is likely to be ingested into each one of them. The depth to which these wells are dug depends on the nature of the soil. They are left unfilled and are covered with RCC slabs of suitable thickness to facilitate vehicular movement on them.

A Percolation/recharge pit is a hand bore made in the soil with the help of an augur and filled up with pebbles and river sand on top. The depth of these pits will be anywhere between 4 and 8 metres depending on the nature of the soil. The pit has to be dug to a depth till a reasonably sandy stratum is reached. The diameter of the pits will be 25 cms. (10 ins.). A square/circular collection chamber with silt arrestor is provided at the top. Instead of filling up with pebbles, which is done only to prevent caving in of the bore, a PVC pipe of 4 or 6 in. diameter can also be inserted for the entire depth.

For further details and technology of Rain Water Harvesting and Water Conservation, please contact
Dr. G.B.K. Rao, CMD, Pragati Group of Companies, Hyderabad on his email : raogbk@gmail.com